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(No Modelfl 2 Sheets-Sheet 1.

G. T. BROWN.

RELIEF VALVE FOR AUTOMATIC AIR BRAKES.

No. 389,193. Patente ept. 11, 1888.

(Jvwwutoz 046/1 @QMM 2 Sheets-Sheet 2.

(N0 Mode-L) 0. T. BROWN.

RELIEF VALVE FOR AUTOMATIC AIR BRAKES. No. 389,193.

Patented Sept. 11

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UNITED STATES PATENT @rrrcn. 7

CHARLES T. BROXVN, OF INDIANAPOLIS,

INDIANA.

RELlEF VALVE FOR AUTOMATIC AIR-BRAKES.

SPECIFICATION forming part of Letters Patent No. 389,193, dated September 11, 1888.

Application filed September 3, 1887. Serial No. 248,712. (No model.)

To all whom, it may concern.-

Be it known that l, Ormnnns T. BROWN, of Indianapolis, Marion county, Indiana, have invented new and useful lniproveznentsin Air- Brakes for Railway-Cars; and Ido declare that the following is a full and accurate description of the same.

In order to render the invention clear, I will first briefly describe the present air-brake apparatus, or one of them, most largely in use.

The air-compressing pump is located upon the engine and is under the immediate con trol of the engineer. Air is compressed into a main accumulator or receiver, and from that it is distributed through suitable train or air pipes,c,to an auxiliary receiver, A, under each car of the train. The triple valve B is placed in said air-pipe. Its office is to permit the air under pressure to enter slowly into said auxiliary reservoir until the pressure therein equals the pressure in the main receiver. Upon any diminution of pressure in the conducting-pipe c, the then superior back-pressure in the auxiliary reservoir A will cause the triple valve to open and admit air to flow from said auxiliary into the air-brake cylinder to operate the brake. To produce this effect, a valve is placed in said air-pipe convenient to the hand of the engineer, whereby the com munication with the main reservoir is cut off at the same moment that it opens an escape for air within said pipe between the triple valve and the engineers valve. Escape of air from the air-pipe c relieves pressure therein and sets up back-pressure in said auxiliary reservoir, and the triple valve is thereby actuated, as set forth. The engineer usually moves his valve slowly, so as not to permit sudden movement of the triple valve; but sometimes he fails to be sufficiently skillful or sufficiently cautious, and sometimes the escape of air from the pipe is the result of accident. Sometimes also, by reason of improper working of the pump governor, orother cause, the engineer suffers the air to be forced into the reservoir with a pressure too high, so that when the brake is operated it will be with too much pressure of the brake-shoes and arrest of therevolution of the wheels. This is highly objectionable, because the tread of the wheel rapidly spoils after that; also, when the brakes have all been set and it is desired to let them off, air is let into the air-pipe 0 under reservoir-pressure; but itfrcquently happens, from g the length of the train and other causes, that the triple valves do not act with desirable proinptness in releasing and discharging the brake-cylinders.

My invention has for its object to prevent the objectionable results arising from overpressure or tardy release by providing a simple attachment which can be applied conveir iently and at small cost to brake-cylinders now in use,and which will be very sensitive,pron1pt, and efficient in act-ion.

Figure 1 is a perspective view of an auxiliary reservoir and the brake-cylinder with the triple valve and the connecting-pipes having my invention applied. Fig. 2 is a longitudinal section of my automatic reliefvalve. Figs. 3 and 4 represent modifications.

D is the brakecylinder, having within it a piston, e, and retractingspringf, which tends to force said piston toward one end of the cylinder, and thereby retract the brakes. When air under pressure is admitted behind said piston, the spring is overcome and the brakes are forced against the wheels.

My relief-valve E opens inward as to the cylinder, and is applied to the brake-cylinder by boring through the head of the same and by screwing therein the end of the valve-case, as shown in Fig. 2. The outer end of the valvecase connects with the air-pipe c, as shown in Fig. 1, and is subjected to air-pipe pressure.

Pressure within the cylinder tends to close the valve E, and pressure within the air-pipe tends to open it; but said valve may be adjusted to balance between these two forces at any desired pressure, and will then stand open when the preponderance of pressure is in the air-pipe, and will stand closed when the pre ponderance of prcssu re is in the cylinder. \Vhen open, it provides free escape for air which enters the cylinder from the auxiliary reservoir under too great pressure, and said escape continues until the pressure has run down to the desired standard, and therefore renders it impossible to apply to the brake pressure sufiicient to lock the wheels and make is flattened by sliding on the rail,and the wheel 1 them slide.

The valve E fits a proper seat, in the valve-case, and is provided with wing-guides to keep it straight and allow free passage for air past it when open. The valve-stem g is rigidly attached at one end to said valve, and at the other end it is provided with a piston, i, which may be sliding or diaphragm, Fig. 2, 3, or 4, and is subjected to air-pipe pressure, which tends to keep the valve off its seat, while cylinder-pressure, if there is any, tends to close it upon its seat. In order to make these forces balance at different pressures, as desired, the valve is made with smaller area than the piston, and a spring, 70, is applied to resist the movement of the piston, so that, supposing the valve and piston to be subjected to the same pressure, the smaller effect on the valve may be made up by the tension of the spring, so as to balance the larger effect on the piston. For instance, suppose the valve and piston areas to be as four to five, and the tension of the spring to be one. The valve and piston will balance when the tension of the spring equals one-fifth theair-pressure,and by varying the tension of the spring the valve and piston may be made to balance at a high or low press ure, as desired.

The valve-case is provided with holes Z for the escape of air which passes the valve.

It will be understood that the structure shown and particularly alluded to may be greatly varied without changing its principle of operation or the effects produced.

The spring 7: may be constructed with a definite tension, and the valve-case and piston-rod may be designed so that said spring will when in place be subjected to a certain standard pressure, adapted to the standard air-pressure preferred; but no change can then be made in said standard without removing the spring and putting others in place. I therefore prefer a structure which will permit a change of spring-tension whenever desired. This may be accomplished in a variety of ways well known to mechanics-as, for instance, that shown in Fig. 3; but in my experiments I have found it convenient to make the change in tension without taking the apparatus apart, and have therefore made the case in two parts screwed together, as at m, and therefore easy to shorten or lengthen. One part has the spring-shoulder n and the other part has the valve-seat. As the valve-stem is not extensible, it follows that to increase the distance between the spring-shoulder and valve seat will increase the tension of the spring. A jamnut, 9, serves to prevent unintentional change in the relative position of the two parts of the valve-case.

and piston will balance, and the valve will close the instant the air-pipe pressure falls below eighty pounds. When it is desired to let off the brakes, it is frequently found that the triple valve, by reason of its delicacy and liability to obstruction by slight causes, does not work promptly and the brakes are not quickly released. This difficulty is overcome by my valve, which is forced open immediately, when the air-pipe is filled again at maximum pressure and the cylinder exhausts independent of the triple valve.

Having described my invention, I claim- 1. In an-autoinatic airbrake apparatus, the combination, with the brake-cylinder, the anxiliary reservoir, the triple valve, and the main air-supp] y pipe, of a valve-case having a valveseat and applied to and communicating with said cylinder, a valve in said casing and opening inwardly into the brake cylinder, a piston of larger area than the valve and connected positively and moving with the same in said case, a spring for moving the piston and valve to close the latter, and a pipe or air-duct con-. necting the said air-supply pipe with the valvecase on the outer side of the piston, substantially as described.

2. In an automatic air-brake apparatus for railway-cars, and in connection with the brakecylinder thereof, the auxiliary reservoir, and the triple valve, a valve, E, arranged to open inwardly as to said cylinder, a spring arranged to close said'valve upon its seat, and a piston in line with and secured rigidly to said valve, and a connection with the air or train pipe communicating with the latter between the triple valve and the engineers valve, whereby when the airpressure in said train-pipe exceeds the standard maximum pressure for the brake-cylinder said valve will be kept open, for the purpose set forth.

R. D. 0. SMITH, J. B. MCGIRR. 

